Traditional vehicle dynamics control systems and ride control systems, such as brake systems and suspension systems, for motor vehicles include hydraulically or pneumatically actuated components associated with two or more wheels of the vehicle. In the case of conventional brake systems, for example, when actuated, the brakes exert a force on a disk or drum which spins in conjunction with the wheel of the vehicle in order to create frictional forces which resist rotation of the wheel. Traditionally, control signals have been transmitted to each of the vehicle dynamics control system's and/or ride control system's components mechanically, or by a hydraulic or pneumatic control circuit. However, it has more recently been proposed to employ a centralized electronic control unit to generate electronic control signals and to use such electronic control signals to control actuation of system components, such as brake actuators. This type of electronic control scheme has become even more prevalent in view of modern vehicle dynamics control systems and ride control systems which now often include not only conventional hydraulic or pneumatic actuator functionality, but also supplemental electronic functions such as antilock protection (ABS) and/or electronic braking force distribution (EBV) between the front and rear axles.
Such electronic control schemes are generally controlled by one or more electronic control units (ECUs), which have a program running thereon which receives various inputs and generates electronic output signals, such as control signals, which are supplied to each of the vehicle system's components. As a more specific example, in electronically controlled braking systems for vehicles, commonly referred to as “brake-by-wire” (BBW) systems, control of the vehicle brakes is achieved by the use of electronic control signals generated at a brake pedal in response to a driver's braking demand and an electronic controller which is adapted to control the supply of fluid under pressure, or more recently electronic power, from a power source to the brakes in accordance with the electronic signals corresponding to the driver's demand.
In modern vehicles, there are typically provided a plurality of electronically controlled vehicle dynamics control systems and ride control systems, or at least one electronically controlled vehicle dynamics control system or ride control system and at least one additional electronically controlled vehicle system. For example, a vehicle may include an electronically controlled electronic brake system (EBS), an antilock brake system (ABS), a suspension system, a traction control system, an anti-slip regulation (ASR) system, a steering system, a stability control system, an electronic stability program (ESP), an adaptive cruise control (ACC) system, a diagnostics system, a trailer interface system, a transmission system, an air management control system, a continuous brake retarder system, an engine control system, etc. It is typical for each of these systems to have separate electronic control units, which may or may not communicate with one another. It would, however, be more desirable and economical for several vehicle systems to be controlled by a single control unit.
A problem exists with this solution, however, in that at certain times, it may be undesirable for the single control unit to control multiple systems, particularly if the control unit is primarily responsible for controlling a critical system. For example, while it may be desirable for the control unit of an electronic braking system to also control one or more auxiliary vehicle systems, such may, at times, interfere with the control unit's primary responsibility of controlling the brake system. As such, at those times when such an interference may occur, it would be desirable for the control unit of the braking system to cease controlling such auxiliary systems.
What is desired, therefore, is a control system for controlling a primary electronically controlled vehicle system which also controls at least one additional auxiliary vehicle system, which controls the auxiliary vehicle system only at certain times when such does not interfere with control of the primary vehicle system, and which gives precedence to controlling the primary vehicle system over the auxiliary vehicle system.